Golf club shaft having multiple metal fiber layers

ABSTRACT

A golf club shaft including a fiber reinforced resin layers and a variety of metal fibers.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to golf clubs and, moreparticularly, to composite resin/fiber golf club shafts.

2. Description of the Related Art

Many substitutes have been introduced for the hard wood shaftsoriginally used in golf club drivers and irons. Early substitutematerials included stainless steel and aluminum. More recently, carbonfiber reinforced resin shafts have become popular. Such shafts aretypically hollow and consist of a shaft wall formed around a taperedmandrel. The use of fiber reinforced resin has allowed golf clubmanufacturers to produce shafts having varying degrees of strength,flexibility and torsional stiffness. As such, manufacturers are able toproduce shafts which suit the needs of a wide variety of golfers.

Nevertheless, manufactures are faced with a variety of design issuesthat have proven difficult to overcome using conventional fiberreinforced resin technologies. For example, some golfers prefer that thecenter of gravity of the shaft be shifted towards the tip of the shaftin order to increase the striking force when the club head impacts thegolf ball. This can be difficult to accomplish with conventionaltechnologies because composite materials are generally light. It is alsopreferable in some instances to increase the kick of the shaft. Oneconventional method of increasing the kick of a shaft is to use a largenumber of graphite fibers that have a very high modulous of elasticity.This method is, however, very expensive. Another method is to alter theshape of the shaft, as is disclosed in commonly assigned U.S. Pat. No.5,957,783. Another design issue is the location of the shaft flex pointand, more specifically, the inability of shaft designers to preciselypredict the location of the flex point when designing a shaft withoutusing excessive amounts of composite material, which can lead to weightand thickness issues.

SUMMARY OF THE INVENTION

The general object of the present invention is to provide a golf clubshaft that eliminates, for practical purposes, the aforementionedproblems. In particular, one object of the present invention is toprovide a golf club shaft with more mass in and around the tip sectionthan conventional shafts. Another object of the present invention is toprovide a golf club shaft with increased kick that does not require alarge number of carbon fibers with a high modulus of elasticity. Stillanother object of the present invention is to provide a golf club shaftwhich facilitates precise location of the flex point.

In order to accomplish these and other objectives, a golf club shaft inaccordance with the present invention includes a plurality of fiberreinforced resin layers and respective pluralities of at least first andsecond metal fibers that are different from one another in at least oneway. Use of the metal fibers allows golf club shafts to manufacturedwith certain properties that correspond to the fibers themselves. Use ofthe metal fibers also allows these properties to be achieved in a mannerthat is easier, more accurate, and more cost effective than can beachieved with conventional fiber reinforced resin manufacturingtechniques.

For example, one embodiment of the present invention includes threedifferent groups of metal fibers, i.e. a plurality of relatively heavymetal fibers, a plurality of relatively stiff metal fibers and aplurality of relatively resilient metal fibers. The ends of the metalfibers are aligned with the tip. The relatively heavy metal fiberspreferably extend about 5 inches to about 8 inches from the tip and areprimarily used to increase the mass of the shaft in and around the tipsection. The relatively stiff metal fibers, which are primarily used todefine the flex point of the shaft, preferably extend about 10 inches toabout 16 inches from the tip. The relatively resilient metal fibersextend at least about 20 inches from the tip and are primarily used toincrease the kick of the shaft.

The above described and many other features and attendant advantages ofthe present invention will become apparent as the invention becomesbetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Detailed description of preferred embodiments of the invention will bemade with reference to the accompanying drawings.

FIG. 1 is a side view of a golf club in accordance with a preferredembodiment of a present invention.

FIG. 2 is an elevation view of the butt end of the golf club shaftillustrated in FIG. 1.

FIG. 3 is an exploded partial view of the tip end of the golf club shaftillustrated in FIG. 1.

FIG. 4 is a partial section view taken through line 4-4 in FIG. 1.

FIG. 5 is a diagrammatic view showing the relative lengths of the metalfibers in the golf club shaft illustrated in FIG. 1.

FIG. 6 is a partial end elevation view of a prepreg sheet used to form ametal fiber layer.

FIG. 7 is an exploded partial section view of a golf club shaft inaccordance with another preferred embodiment of the present inventiontaken from the same position as FIG. 4.

FIG. 8 is an exploded partial section view of a golf club shaft inaccordance with still another preferred embodiment of the presentinvention taken from the same position as FIG. 4.

FIG. 9 is an exploded partial section view of a golf club shaft inaccordance with yet another preferred embodiment of the presentinvention taken from the same position as FIG. 4.

FIG. 10 is an exploded partial section view of a golf club shaft inaccordance with another preferred embodiment of the present inventiontaken from the same position as FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following is a detailed description of the best presently knownmodes of carrying out the invention. This description is not to be takenin a limiting sense, but is made merely for the purpose of illustratingthe general principles of the invention. The scope of the invention isdefined by the appended claims.

As illustrated for example in FIG. 1, a golf club shaft 10 in accordancewith a preferred embodiment of the present invention includes a hollowshaft 12, a grip 14, and a club head 16. The exemplary shaft 12 isdivided into three sections—the grip section 18 which is covered by thegrip 14, the tip section 20 which supports the club head 16, and themain body section 22 which extends from the distal end of the gripsection to the proximal end of the tip section. In the illustratedembodiment, the grip section 18 is substantially cylindrical, the tipsection 20 is substantially cylindrical, and the main body section 22has a substantially constant taper. The present invention is not,however, limited to such a configuration. Other grip section, tipsection and main body section configurations and shapes, such as thosedisclosed in commonly assigned U.S. Pat. Nos. 5,944,618 and 5,957,783,both of which are incorporated herein by reference, may also beemployed.

The fiber reinforced resin composite portions of the exemplary shaft 12may be formed in conventional fashion by wrapping multiple layers(typically 10-20 layers total) of a fiber reinforced resin compositeover a mandrel until the desired wall thickness is obtained. Referringmore specifically to FIGS. 2 and 3, the exemplary shaft 12 includeslayer groups 24, 26, 28 and 30 which are preferably oriented atdifferent angles with respect to the longitudinal axis of the shaft 12.Each of the groups includes a plurality of fiber reinforced resinlayers. The fibers within the respective layers of each group areparallel to one another. The fibers 24 a and 26 ain the layers withingroups 24 and 26 are angled from 30-90 degrees with respect to thelongitudinal axis, while the fibers 28 a and 30 a in layer groups 28 and30 are parallel to the longitudinal axis. Other layer and layer groupcombinations may also be employed in embodiments of the presentinvention. For example, layer groups 24 and 26 may be combined (a totalof 5-10 layers, for example) and the individual layers arranged suchthat the fibers in successive layers are oriented at different angleswith respect to the longitudinal axis.

It should be noted that the dimensions of the shafts illustrated in thedrawings are exaggerated. Commercial embodiments of the shafts describedherein may range from about 33 inches to about 46 inches in overalllength. With respect to the tip section 20, the length may range fromabout 3 inches to about 7 inches and the outer diameter (OD) may rangefrom about 0.370 inch to about 0.500 inch for irons and from about 0.335inch to about 0.500 inch for woods. The length of the grip section 18may range from about 6 inches to about 10 inches. The exemplary gripsection may be either substantially cylindrical (as shown) with an OD ofabout 0.58 inch to about 0.62 inch or tapered from an OD of about 0.81inch to about 1.0 inch at the butt to an OD of about 0.55 inch to about0.70 inch at the grip section/main body section intersection. The wallthickness is preferably between about 0.6 mm and about 1.5 mm.

In accordance with the present invention, the exemplary shaft 12 alsoincludes a number of metal fiber layers. As illustrated for example inFIGS. 3-5, the preferred embodiment of the present invention includesthree metal fiber layers 32, 34 and 36 extending proximally from the tipof the tip section 20. Layers 32, 34 and 36 include respectivepluralities of metal fibers 32 a, 34 a and 36 a. The metals from whichthe fibers 32 a, 34 a and 36 a are formed, as well as the length andlocation of the layers, will depend of the desired result. Each metalfiber layer 32, 34 and 36 in the preferred embodiment includes metalfibers formed from a different metal than the other two layers, and eachextends from the tip to regions located different distances from thetip.

More specifically, metal fiber layer 32 in the exemplary embodimentillustrated in FIGS. 3-5 is located in region C between fiber reinforcedresin layers 24 and 26. Metal fibers 32 a are formed from a relativelyheavy metal such as tungsten and extend about 5 inches to about 8 inchesfrom the tip. Lead is another suitable metal. The primary function ofthe relatvely heavy fibers 32 a is to increase the mass of the shaft inand around the tip section 20. Metal fiber layer 34, which includesfibers 34 a formed from a relatively stiff metal such as boron, islocated in region B between fiber reinforced resin layers 26 and 28 andextends about 10 inches to about 16 inches from the tip. The relativelystiff metal should also be relatively light. Another suitable metal isberyllium. The primary purpose of the relatively stiff fibers 34 a is todefine the flex point of the shaft. Metal fibers 36 a are formed from arelatively resilient metal (i.e. a metal with a relatively high modulusof elasticity) such as titanium and extend from the tip to at leastabout 20 inches from the tip and, if desired, all the way from the tipto the butt. Metal fiber layer 36 is located in region A between fiberreinforced resin layers 28 and 30. The relatively resilient metal shouldalso be relatively light. The primary purpose of the relativelyresilient fibers 36 a is to increase the kick of the shaft.

Referring to FIGS. 3 and 6, the metal fiber layers 32, 34 and 36 arepreferably pre-preg sheets formed by winding the metal fibers 32 a, 34 aand 36 a onto resin pre-impregnated fiberglass sheets (or “scrim cloth”)32 b, 34 b and 36 b. Although the actual dimensions may vary, thefiberglass sheets 32 b, 34 b and 36 b are relatively thin (preferablyabout 0.02 mm to about 0.05 mm thick) with a weight of about 20 g/m².The respective diameters of the metal fibers 32 a, 34 a and 36 a in thepreferred embodiment may range from about 0.002 inch to about 0.008 inchand are preferably about 0.004 inch to about 0.006 inch. The density ofthe metal fibers may range from about 10 fibers/inch to about 200fibers/inch and is preferably about 20 fibers/inch. Alternatively, themetal fibers 32 a, 34 a and 36 a may be incorporated into a layer ofresin to form a composite pre-preg sheet. In either case, each pre-pregsheet is wrapped around the appropriate fiber reinforced resin layerduring manufacture of the shaft.

Shafts in accordance with present invention are not limited to theexemplary configuration illustrated in FIGS. 3-5. Metal fiber layers 32,34 and 36 may be relocated relative to the fiber reinforced resin layergroups 24, 26, 28 and 30 and relocated relative to one another. Inaddition, more than one metal fiber layer may be located in a singleregion between a given pair of fiber reinforced resin layer groups.Metal fiber layer 32, which includes relatively heavy fibers 32 a, maybe located in regions A, B, C (as shown) or D, either alone or incombination with one or both of the other metal fiber layers. Metalfiber layers 34 and 36, which respectively include relatively stiff andrelatively resilient fibers 34 a and 36 a , may be located in layers Aand B either alone (as shown), together and/or in combination with metalfiber layer 32.

The performance properties of shafts in accordance with the presentinvention may be adjusted through variations in the respectivelocations, lengths, metal fiber densities and other properties of themetal fiber layers 32, 34 and 36. For example, the greater thecircumference of the layer, the greater the number of fibers and,therefore, the greater the effect of the metal fiber layer. Thus, for agiven fiber density, the location of the metal fiber layer 32 willdetermine the weight of the metal fiber layer. The weight of metal fiberlayer 32 may also be varied by varying the density of the fibers 32 awithin the layer and/or the diameter of the fibers. Similar adjustmentsmay be made with respect to metal fiber layers 34 and 36. In addition,in alternative embodiments, any one of the layers may be omitted if theperformance property created thereby is not desired.

By way of example, but not limitation, shafts having some of thepossible alternative configurations are illustrated in FIGS. 7-9. Theexemplary shaft 38 illustrated in FIG. 7 includes relatively heavy metalfibers 32 a that are located in region B and relatively stiff andresilient metal fibers 34 a and 36 a that are both located in region A.As compared to shaft configuration illustrated in FIGS. 3 and 4, shaft38 will have a greater mass in and around the tip section and will bealso be stiffer.

The exemplary shaft 40 illustrated in FIG. 8 includes relatively heavymetal fibers 32 a that are located in region D, relatively stiff metalfibers 34 a that are located in region A, and relatively resilient metalfibers 36 a that are located in region B. As compared to shaftconfiguration illustrated in FIGS. 3 and 4, shaft 40 will have a lessermass in and around the tip section.

As illustrated for example in FIG. 9, exemplary shaft 42 includesrelatively heavy metal fibers 32 a that are located in region A,relatively stiff and resilient metal fibers 34 a and 36 a that are bothlocated in region B. Shaft 42 will have a greater mass in and around thetip section than the shafts illustrated in FIGS. 3 and 4, 7 and 8.Additionally, as compared to the shaft illustrated in FIGS. 3 and 4,shaft 42 will have less kick.

The exemplary embodiment 44 illustrated in FIG. 10 is substantiallysimilar to that illustrated in FIGS. 3 and 4. Here, however, theouter-most fiber reinforced resin layer group 30 has been removed andreplaced by one or more resin pre-impregnated fiberglass sheets 46. Oneadvantage of this embodiment is that the metal fibers 36 a , which arenot visible to the user through the outer-most fiber reinforced resinlayer group 30, will be visible through the resin pre-impregnatedfiberglass sheet(s) 46. The outer-most fiber reinforced resin layergroup in any of the other exemplary embodiments described herein mayalso be replaced with one or more resin pre-impregnated fiberglasssheets.

The present invention may be practiced with any of the materialstypically used to produce composite resin/fiber golf club shafts.Suitable resins include, for example, thermosetting resins or polymerssuch as polyesters, epoxies, phenolics, melamines, silicones, polimides,polyurethanes and thermoplastics. Suitable fibers include, for example,carbon-based fibers such as graphite, glass fibers, aramid fibers, andextended chain polyethylene fibers. After the successive layers of fiberreinforced resin are wrapped around the mandrel, the shaft is cured inan oven. Curing times and temperatures depend on the polymer used in thecomposite and are well known to those of skill in the art.

Shafts and rods having fiber reinforced layers and metal fiber layers inaccordance with the present inventions also have application in devicesother than golf club shafts. For example, baseball bats, bike tubes,sail masts and fishing rods may be formed with the above described layercombinations.

Although the present invention has been described in terms of thepreferred embodiment above, numerous modifications and/or additions tothe above-described preferred embodiments would be readily apparent toone skilled in the art. It is intended that the scope of the presentinvention extends to all such modifications and/or additions and thatthe scope of the present invention is limited solely by the claims setforth below.

1. A golf club shaft, comprising: a plurality of resin layers defining atip, a tip section, a main body section, a grip section, and a butt; anda plurality of first metal fibers defining a first length locatedbetween two of the resin layers; and a plurality of second metal fibersdefining a second length located between two of the resin layers, thesecond length being greater than the first length. 2-35. (canceled)